Transformer read-only storage construction



March 11, 1969 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet of12 FIG. 1

12c 12D |2E 12F 9c 90 9E 9F INVENTORS CHARLES E. OWEN ANTONY PROUDMANDANIEL M TAUB WILLIAM A. WARWICK I CwiCKb-n ATTORNEY l March 11, 1969 c.E. OWEN ETAL TRANSFORMER'READONLY STORAGE CONSTRUCTION Sheet g of 12Fild Nov. 20, 1964 FIG. 3

March 11 1 969 O c. E. OV\A/EN ETAL TRANSFORMER READ-ONLY STORAGECONSTRUCTION Filed Nov. 20 1964 Sheet 3 of 12 FIG. 7

M p 550mm Jmufim p Q m UUUUU U MW D nmmuflmmmmzm Mil I M 3 i C. E. OWENETAL March 11, 1969 TRANSFORMER READ-ONLY STORAGE CONSTRUCTION FiledNov. 20, 1964 Sheet 4 of 12 FIG. 8

E. w Q Ufi/ v V 0 U U H o Q U U Tll l H w fi U? M a y 5 FIG. 9

March 11, 1969 Filed NOV. 20, 1964 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Sheet 6' of 12 FIG. 10

FIG. 11

March 11, 1969 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet 6of 12 FIG. 20 /2 [/N 1 W t /2 Q FIG. 21

FIG. 13

C. E. OWEN ETAL TRANSFORMER READ-ONLY STORAGE CONSTRUCTION March 1 1,1969 Filed Nov. 20, 1964 Sheet FIG. 15

March 11, 1969 c, OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet 8of 12 FIG. 16

FPL PL RL RL /NPU7 CURRENT f T/ME OUTPUT CURRENT HB/NARY V) A T/MEOUTPUT CURRENT (BM/AR) o) A A A v r/ME FIG. 17

March 11, 1969 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 sheet 9of 12 FIG. 18

March 11, 1969 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet /0of 12 FIG. 22

A78 KI] LZZZ'IIIII- FIG. 23

March 11, 1969 c. E. OWEN ETAL 3,432,830

TRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed NOV. 20, 1964 Sheet of12 FIG. 24 43 49 mtlmd FIG. 43 49 42 I Mai-Ch 11, 1969 5. OWEN ETALTRANSFORMER READ-ONLY STORAGE CONSTRUCTION Filed Nov. 20, 1964 Sheet 5of 12 FIG. 27

vvvvvvvvvvgvvv United States Patent O 3,432,830 TRANSFORMER READ-ONLYSTORAGE CONSTRUCTION Charles E. Owen, Eastleigh, Antony Proudman,Awbridge, near Romsey, Daniel M. Taub, Winchester, and William A.Warwick, South Wonston, near Winchester, England, assignors toInternational Business Machines Corporation,'Armonk, N.Y., a corporationof New York Filed Nov. 20, 1964, Ser. No. 412,665 U.S. Cl. 340-174 5Claims Int. Cl. Gllb 5/00 ABSTRACT OF THE DISCLOSURE An improvedread-only memory is disclosed of the type in which each bit position ofthe memory has a transformer core that couples a large number of primarywindings to a single secondary winding. The primary windings areinterconnected to form words of the memory and selecting a particularword produces a pattern of signals on the secondary windings. Theprimary windings for each word are formed on a longitudinal tape thathas apertures for receiving the legs of the transformers at each bitposition. A structure is disclosed that reduces the ringing that canoccur in a device of this type. The longitudinal conductors in adjacenttapes are staggered so as to reduce capacitive coupling between thelongitudinal conductors. Each transformer core is fitted with a closedloop having an appropriate resistance to damp the ringmg.

between such longitudinal conductors, thus reducing the' ringing. Italso includes a technique for damping oscillations by fitting eachtransformer core with a closed loop of resistance conductor.

ENVIRONMENT OF THE INVENTION The invention operates with a transformerread-only storage device such as described in the following publication:

D. M. Taub and B. W. Kington, The Design of Transformer (Dimond Ring)Read-Only Stores, IBM Journal of Research and Development, vol. 8, No.4, September 1964, pp. 443-459.

Such a transformer read-only store includes a group of U-shaped coresmounted in a row and equipped with I-shaped keepers that close theinductive loop. The I- shaped keepers each are equipped with a secondarywinding which connects to sense amplifiers for output. The U-shapedcores are inserted through slots in each of a group of flexible tapeswhich carry the primary winding conductors. The flexible tapes aresuitably punched so that the primary conductors selectively pass insidethe particular core or outside the particular core to give output values1 and 0 respectively. There may be, for example, sixty-four primaryconductor tapes for a group of sixty cores. That is, the cores might beequipped to produce sixty-four words of information, each word havingsixty bits.

When the word associated with a given conductor tape is selected anddriven, normal transformer action provides outputs on the secondarywindings. If the primary conductor passes inside the core, transformeraction provides an output on the secondary conductor. If the conductoron the second core does not pass through the core but rather passesoutside it, the flux coupling is such that the transformer action doesnot occur and there is no output on the secondary conductor. The outputcondition is given the 1 value; the no-output condition is given the 0value.

Because of the great inductances and capacitances involved, thetransformer read-only storage device is subject to ringing oscillations,which can be aggravated by certain types of data arrangements.

CHARACTERISTICS OF THE INVENTION The invention is a technique forminimizing oscillatory noise transients in a transformer read-onlymemory, by controlling the production of noise on the input tapes and bydissipating noise actually produced in a winding about the coresthemselves.

OBJECTS The object of the present invention is to provide an improvedtransformer read-only memory by reducing ringing oscillations.

Another object of the invention is to reduce capacitive coupling betweenadjacent input tapes of a transformer read-only storage.

Another object of the invention is to dissipate noise transientsdeveloped by an individual transformer in a transformer read-onlystorage.

FEATURES A feature of the invention is the selective offsetting ofadjacent input tapes of a transformer read-only storage to minimizecapacitive coupling between drive windings on adjacent tapes.

Another feature of the invention is the provision of a shorted turn ofresistance conductive material about each core of a transformerread-only storage device so as to dissipate noise transients within theconductive loop.

ADVANTAGES An advantage of the invention is the provision to atransformer read-only storage device of a more noisefree signal.

SUMMARY OF THE INVENTION The invention relates to construction featuresfor reducing ringing oscillations in a read-only storage device of thetransformer type. A transformer read-only storage device is particularlysubject to ringing because of the large inductances of the transformercores 10 and the large capacitances of the input conductors 11 which arecarried on closely spaced plastic tapes 7 and selectively punched fordata content.

Oscillations are minimized by staggering the placement of conductors11A, 11B and 11C respectively on tapes 7A, 7B and 70. Correspondingconductors on adjacent tapes are thus kept at a distance considerablygreater than the thickness of the tapes, greatly decreasing their mutualcapacitance.

An auxiliary tape 8 is included to provide damping of the individualcores. Areas of resistive material 9 are arranged in closed loops aboutthe holes in tape 8 through which the core legs are to pass. Theresistance of each loop 9 is -a R /n where:

a is the number of loops linking one transformer core n is the number oftransformers R is the resistance value required to provide criticaldamping to the inductance and capacitance present.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of a preferred embodiment of the invention, as illustratedin the accompanying drawings.

In the drawings:

FIGURE 1 illustrates a transformer read-only storage device according tothe invention;

FIGURE 2 shows a number of transformer cores connected to store a dataword according to the invention;

FIGURE 3 shows the structure of a transformer core and a method ofstoring data words on a tape according to the invention;

FIGURES 4 and 5 indicate the effect of plating the transformer coreswith copper according to the invention;

FIGURE 6 shows a stack of tapes arranged for use in the T.R.O.S.according to the invention;

FIGURE 7 shows a complete tape for use in T.R.O.S. prior to programming;

FIGURE 8 shows one method by which the tape may be programmed to storedata words;

FIGURE 9 shows another method by which the tape may be programmed tostore data words;

FIGURE 10 shows an improved tape for use in the T.R.O.S. according tothe invention;

FIGURES 11 and 12 show one method of connecting a tape to drive andselect circuitry;

FIGURE 13 shows another method of connecting a tape to drive and selectcircuitry;

FIGURE 14 shows the preferred method of stacking tapes in T.R.O.S.according to the invention;

FIGURE 15 is a side elevation of FIGURE 14 in the direction of the arrowA;

FIGURE 16 shows a schematic representation of a portion of the T.R.O.S.with a pattern of stored information which aggravates oscillations;

FIGURE 17 shows output pulses received in response to an input pulse forthe two values of information stored;

FIGURE 18 represents the equivalent circuit of FIG- URE 16;

FIGURE 19 is another form of the equivalent circuit shown in FIGURE 18;

FIGURE 20 is a simplified form of FIGURE 19;

FIGURE 21 is a simplified form of FIGURE 20;

FIGURE 22 shows a portion of a resistive tape used to damp oscillationsin the T.R.O.S. according to the invention;

FIGURE 23 shows how oscillations are eliminated by serially damping thetransformer cores used according to the invention;

FIGURES 24, 25, and 26 show various staggers of primary windings used inT.R.O.S. to reduce inter-primary capacitive coupling according to theinvention;

FIGURE 27 shows an exploded view of the T.R.O.S. module according to theinvention;

GENERAL DESCRIPTION FIGURE 1 illustrates a read-only storage deviceconstructed according to the invention. Transformer core 10 is equippedwith an output conductor 12 (secondary winding) and several data tapes7. The data tapes include ladder configuration conductors 11 which areselectively punched to direct electrical currents selectively through ornot through the cores for 1 and 0 values.

Data tapes 7A, 7B and 7C are nonidentical in that the ladderconfiguration conductors 11A, 11B and 11C which they carry are laterallyoffset. This staggering of conductors provides sufiicient dielectricspacing between conductors on adjacent tapes to reduce capacitance andthus reduce ringing.

A fourth type of tape, tape '8, contains areas 9 of conductive materialarranged to form resistive loops about the cores 10. The resistances ofthese loops are calculated to provide critical damping to the cores.

A binary bit of information is represented in the transformer read-onlystore (T.R.O.S.) by the presence or absence of a primary winding on acurrent transformer.

This is illustrated in FIGURE 2 which shows several transformer cores10A-10F, a primary winding 11 and several secondary windings 12A12F.Primary winding 11 bypasses the cores 10C, 10D and 10F; therefore acurrent pulse on the primary winding 11 produces no out put on theirsecondary windings 12C, 12D, 12F. This represents binary 0 bits ofinformation. Primary winding 11 threads through cores 10A, 10B and 10Eand so a current pulse on the winding 11 will produce an output signalon their secondary windings 12A,.12B and 12E. This represents binary 1bits of information. A data word is made up of a number of thesetransformers having a common primary winding 11 which threads, or doesnot thread, through the cores 10 depending on the binary bits ofinformation required to make up the data word. FIGURE 2 shows sixtransformers wired to store the data word 1 10 010.

SPECIFIC DESCRIPTION In practice, it has been found convenient tomanufacture the transformer cores in two parts. This makes the assemblyof the transformer read-only store much simpler as will be seen from thefollowing description. A transformer core is shown in FIGURE 3 and isseen to consist of a U-shaped part 13 and an I-shaped part 14. TheIasha-ped part 14 is used to close the open end of the U-shaped part 13and so produce a transformer core which is rectangular in shape. Thefigure also shows a flexible insulating carrier 15 having two rows ofapertures 16 and 17 punched along its length. The two limbs of theU-shaped part 13 of a core are shown threaded through two of theseapertures, one in row 16 and the other in the corresponding aperture inrow 17. Although, for the sake of clarity, only one transformer core isshown in position, it will be understood that the portion of the carrier15 shown in the figure has sufficient apertures 16 and 17 to accommodatesiX such cores.

The primary winding is deposited, or otherwise formed as a thinconductive strip 18 on the surface of the carrier 15 so that itby-passes or threads through the assembled cores depending upon theinformation to be stored. It is now evident why it is convenient tomanufacture the core in two parts. The open end of the U-shaped part 13is closed with the I-shaped part 14 which carries a sense winding 19which is, in fact, the secondary winding of the transformer.

Since both limbs of the Uashaped part 13 of each core in the assemblypass through apertures in the carrier 15, a further primary winding isprovided which threads or by-passes the cores to store a second dataword. This further primary winding is also deposited as a thinconductive strip 21 on the surface of the carrier 15.

Two data words have thus been stored on the carrier 15 using the sametransformer cores for both. Read out is accomplished by applying acurrent pulse to one or the other of the strips 18 or 20 whereupon thedata word stored by the selected strip is produced as a parallelcombination of signals and no-signals on the sense windings 19 of thecores.

Before continuing with the description of the construction of thetransformer read-only store, the final form of the transformer cores tobe used will be discussed in detail.

The U-shaped parts 13 and I-shaped parts 14 which form the magneticpaths of the current transformers consist of a saft ferrite material (asdistinct from square loop ferrite material) and are coated with a thinlayer of copper plating. This layer of copper is provided to reduce theleakage flux associated with the primary and secondary windings. Theplating permits flux which is parallel to its plane to enter theferrite, but flux which is perpendicular to it to be cancelled. Theeffect can be best understood by reference to FIGURES 4 and 5.

In FIGURE 4 a magnetic fiux B having a magnetizing force H is shownperpendicular to a copper sheet 22. If

the copper is assumed to be a perfect conductor, then eddy currents inthe copper produce an equal and opposite magnetic force to H such that Bis cancelled. A perpendicular component of magnetic flux (leakage flux)will not, therefore, pass through a perfectly conducting sheet of metal.

The conducting sheet 22 has no effect on a parallel component of flux Bas shown in FIGURE 5.

This principle of screening is applied to the transformer cores byplating them with copper. The flux enters the ferrite quite easily, butafter entering, if it tries to take a shorter reluctance path, sayacross the window of the core, then its perpendicular component iscancelled. The flux in the ferrite can, therefore, only follow a pathoutlined by the copper and so, theoretically, no leakage flux can existbetween any two windings on the core.

In practice, however, the plating has to be provided with a gap 23 whichextends around the U-shaped part 13 of each core to prevent the copperplating acting as a shortcircuited turn. Some leakage of flux can occurat the gapping positions. The gap 23 can be made on the edge of thecores, 'but the most favored position is in the center of the face asshown in FIGURE 3. The face of the I-shaped part 14 which makes contactwith the open end of the U- shaped part is left unplated and so no gapis required on the member.

The gap 23 in the copper can be made by one of several techniques; forexample, sawing (ultrasonic or mechanical) and grinding. Whichevermethod is used, care has to be taken that the cut does not becomecontaminated with low resistivity foreign matter.

Two soft ferrite materials from which the transformer cores can be madeare manganese zinc ferrite and nickel zinc ferrite. Cores made frommanganese zinc ferrite must be coated with a layer of an insulatingmaterial to prevent the copper layer from making contact with theferrite. This is because manganese zinc ferrite has a high per mittivityand low resistivity and if the copper made contact with this material,it would act as a single turn secondary winding with the ferrite, thatis, as a very low series resistance. A suitable insulating material isaraldite which has the additional advantage of being a strong adhesive.The coating with araldite is not necessary for cores made of nickel zincferrite. After plating the cores are covered with a protective coatingwhich helps to prevent peeling and corrosion of the plating and alsoimproves the appearance of the cores.

A plurality of flexible carriers 15 or tapes, as they will hereinafterbe called, are then taken, each identically punched with rows ofapertures 16 and 17, and are superimposed one upon the other so that therows of apertures are in alignment. The limbs of the U-shaped parts 13of the transformer cores are then passed through corresponding aperturesin all of the plurality of tapes 15 as shown in FIGURE 6. Each tape 15has two primary windings in the form of conductive strips 18 and 21which store two data words on each tape as has already been explained.The number of tapes 15 superimposed one on the other is limited only 'bythe size of the transformer core and in the preferred embodiment of thisinvention, one hundred and twenty-eight such tapes are used. The numberof transformers required is determined by the number of bits required tomake the data word. A word of sixty bit length has been found sufficientand so each row 16 and 17 contains sixty apertures to receive sixtyU-shaped parts 13 of the cores. Thus with one hundred and twentyeighttapes arranged in a stack and threaded by sixty transformers, a storagecapacity of two hundred and fifty-six words of sixty bit length isobtained. Information is read out by passing a drive current along oneor other of the conductive strips 18 or 21 on a selected tape 15 and theselected word is received as a parallel combination of signals andno-signals on the sixty sense windings 19 wound on the I-shaped part 14of the cores.

It would be an arduous task if the conductive strips 18 and 21 had to beseparately deposited on each tape 15 to thread through or by-pass thecores according to the information words to be stored. This difficultyis overcome in the manner described below with reference to FIG- URE 7.

Onto each tape 15, which has been identically punched with two rows ofapertures 16 and 17, are deposited two identical ladder networks 24 and25. These ladder networks are of such dimensions and so positioned onthe tape that each aperture in the row of apertures 16 is symmetricallypositioned between separate rungs of the ladder network 24 and eachaperture in the row of apertures 17 is symmetrically positioned betweenseparate rungs of the ladder network 25. It only remains now to removethe parts of the ladder networks on the inside or outside of eachaperture so that two continuous conductors are formed from one end ofthe tape 15 to the other that thread or by-pass the transformer cores,depending on the two data words to be stored on each tape 15. In orderto show the ladder network to best advantage, only one transformer core13 is shown in position in FIGURE 7.

Each tape 15 is also provided with an extension 26 at one end and anextension 27 at the other end. Connecting leads 28 and 29 are depositedonto the extensions 26 to connect the ends of the ladder networks 24 and25 to tags 31 and 32 provided at the end of the extension. Similarly,connecting leads 33 and 34 are deposited onto the extension 27 toconnect the other ends of the ladder networks 24 and 25 to tags 35 and36 provided at the end of that extension. In use, the tags 31, 32, 35and 36 are connected to input and output circuitry for selection andread-out of a particular data word stored.

Finally, each tape 15 is provided with a row of sprocket holes 37arranged symmetrically along the length of the tape between the rows ofapertures 16 and 17. One sprocket hole is provided between thecorresponding aperture in the rows 16 and 17 so that the tape 15 can beadvanced in a machine step by step for removing unwanted portions of theladder networks 24 and 25.

The removing of portions of the ladder networks 24 and 25 to form thetwo continuous conductive strips from one end of the tape to the otherand to give the required data words is known as programming. Tapeprogramming can be carried out in a number of ways. The unwantedportions of the ladder networks may be punched out. For example, tostore a binary 1 bit of information in a particular transformer core theside of the ladder network passing outside the limb of that core must bebroken. A current pulse applied to the programmed ladder network willthen pass through the core and an output representing a binary 1 bitwill be received on the sense winding of that core.

A portion of the tape 15 which has been programmed by punching is shownin FIGURE 8. The punch used in this instance is triangular in shape andof such a dimension that the apex of the punch hole 38 extends asufficient distance to break the side of the ladder network which isunwanted. The tape is fed through a conventional punching machine step'by step and one or the other side of the two ladder networks 24 and 25is punched out.

The shape of the punch hole 38 is immaterial, providing it cuts throughthe unwanted part of the networks. Only one transformer core has beenshown in position in this figure and the binary bits of informationstored by the punching are indicated. For example, a current pulseapplied to the left hand side of the programmed ladder network 24 of thetape 15 shown in FIGURE 8 will pass through the first and second cores(binary 1 'bits), by-pass the third and fourth cores (binary 0 bits),pass through the fifth (binary 1 bit) and by-pass the sixth core (binary0 bit). Thus the data word 1 1 0 0 1 0 will be received on the six sensewindings wound around the I-shaped parts of the six transformer cores ofthe 7 tape. Similarly, the data word 1 0 1 1 0 is stored by theprogrammed ladder network 25 of the tape.

Another method of programming the tape is by etching. This isparticularly useful when a large quantity of tapes are required all ofwhich contain the same information. The method used in this case isknown as a photoresistive etch process. In this method a number ofcopies is made of the master negative of the unprogrammed tape. Each ofthe negatives is then altered by blanking out the appropriate positionson the two ladder networks for binary 1 bits or binary 0- bits to form aprogrammed negative. A normal photo-resistive etch is then carried outon the tape which is first completely coppered on one surface. A tapeprogrammed by this etching technique is shown in FIGURE 9.

Finally, the tape can be programmed by directing a fine abrasive, pumpedby air pressure through a nozzle, onto the unwanted portions of theladder networks. The programmed tape would also look like that shown inFIGURE 9.

The read only store so far described consists of a number of tapes eachstoring two words of sixty bit length. Because of the construction ofthe tape, connections have to be made at each end of every tape in orderto select and read out a particular data word. Another point which maybe considered as a disadvantage is that the length of each tape 15 isdetermined by the number of bits in each word to be stored on the tape.In this case (a word length of sixty bits) the tape would have to belong enough to accommodate sixty transformers in a line. Both thesedrawbacks have been overcome by designing a tape as shown in FIGURE 10.

This tape, labelled 39, is so designed that it still stores two datawords each of sixty bits and yet its length is reduced by approximatelyhalf with only a small increase in width. Connections for selecting andreading out a word are only required at one end.

In this arrangement, the transformer cores are provided in two parallelrows along the tape and half of each data word is stored in one row andthe other half in the other row. As in the previous case, each tape 39is identical before the programming operation. Each tape 39 is providedwith four rows of apertures 41, 42, 43 and 44 to accommodate the limbsof the U-shaped parts 13 of the two rows of transformer cores. Each rowof apertures is provided with an enclosing ladder network as before. Theladder networks for the rows of apertures 41, 42, 43 and 44 have beenlabelled 45, 46, 47 and 48 respectively. A row of sprocket holes 49extend along the length of the tape having two rows of aperturessymmetrically positioned on each side.

The ladder network 45 is connected at one end of the tape 39 to theladder network 48 by a conducting strip 51. Similarly, the laddernetworks 46 and 47 are connected at the same end of the tape byconducting strip 52. At the other end of the tape an extension lead -3is provided which carries on its free end four tags 54, 55, 56 and 57.These tags 54, 56 and 57 are required for connecting the tape to drivingand selecting circuitry necessary for read-out and are connected byconnecting leads 58, 59, 61 and 62 to the free ends of the laddernetworks 45, 46, 47 and 48 respectively.

The tapes are then programmed so that each stores the required two datawords. Programming is the same as previously described for the tape 15shown in FIGURE 7, that is, by punching or otherwise removing theunwanted portions of the ladder networks; the tape being fed step bystep in a machine by means of the row of sprocket holes 49. Afterprogramming, each tape carries two data words of sixty bits. One wordextends down ladder network 45 and up ladder network 48 and will becalled the A-word on the tape. The other word extends down lad dernetwork 46 and up ladder network 47 and will be called the B-word on thetape. Thus an A-word is read out by passing a current pulse through theladder networks which extend from the tag 54 to the tag 57 and a B-wordis read out by passing a current pulse through the ladder networksextending from tag 55 to tag 56. A few U-shaped parts 13 of the coreshave been shown in position in order to indicate the position of the tworows of transformer cores on the tape and the ladder networks are shownprogrammed with a repetitive pattern.

Again, it is envisaged that a large number of these tapes 39 will besuperimposed one upon the other so that their rows of apertures are inprecise alignment and the same transformer cores can be used for all ofthe tapes. Connections have to be made between the driving and selectingcircuitry or circuit boards and the tags on each tape. The circuitboards will be described in detail later, it being sufficient at thisstage only to say that they exist. The connections can be made in one ofseveral ways, two of which are described below.

The portion of the extension lead 53 carrying the tags 54, 55, 56 and 57is looped as shown in FIGURE 11 and FIGURE 12 and passed through a slotin a board 64. The tags are then flow soldered onto leads 65 from whereconnections can be made.

Another method is to provide pins on each tape so that they can beplugged into holes in the connector board and then soldered in position.This is the method used in this invention. FIGURE 13 shows theconnecting pins 66, 67, 68 and 69 connected to the tags 54, 55, 56 and57 on the extension lead 53 of a storage tape. Each pin is provided withtwo lugs 71 and 72 which pass through the tape extension lead 53 and arebent over to make contact with the tag member to which the pin is to beconnected. Good electrical contact is made between the pins and the tagsby soldering the lugs 71 onto the tags (the solder connection is notshown). This also increases the mechanical strength of the connection.

The large number of connections that are required in a tape deckcontaining 128 tapes present quite a problem. The extension leads 53 ofthe tapes are fanned out and connections are made to more than onecircuit board but even so the circuit boards would have to be largerthan desired to accommodate all these connections. The solution to thisproblem resides in the fact that the rows of apertures 41, 42, 43 and 44are symmetrically positioned in the tape with respect to the row ofsprocket holes 49 and to each other. That is, when two tapes are placedtogether with one of the tapes inverted, then the five rows of aperturesstill register. FIGURE 14 shows the tape deck (one hundred andtwenty-eight tapes) which has been divided into two halves, each halfcontaining the same number of tapes (sixty-four tapes). One half of thetape deck 39a is shown with the extension leads 53 uppermost while theother half 39b is shown inverted and positioned with the rows ofsprocket holes 49 in precise alignment with the sprocket holes in thetapes 39a. In view of the symmetry of the tapes, the rows of apertures41 and 42 in the upper deck of tapes 39a are in alignment with rows ofapertures 44 and 43 in the lower deck of tapes 3%. Similarly the rows 43and 44 of the upper deck 39a are in alignment with rows 42 and 41 of thelower deck 3%. FIGURE 15 is an end view of FIGURE 14 seen in thedirection of the arrow A and is included in order to show the alignmentof the apertures on the two halves of the tape deck. By aligning the rowof sprocket holes 49 along the center of each tape the overlap shown inFIGURES 14 and 15 need not occur. It is for this reason that no overlapis shown in later figures.

The extension leads 53 can now be connected to both edges of a circuitboard or circuit boards with considerably less congestion thanpreviously. This method of stacking the tape deck presents no greatproblems to the driving and selection circuitry as will be apparent whenthe structure of the circuit boards are discussed later.

The tapes 39 are of insulating material but the ladder networks areconductive material, for example, copper. It is therefore seen that withthe arrangement shown in FIGURES 14 and 15 the conductive networks onthe two central tapes will be touching one another. To prevent this asingle insulating sheet having identical punchings as a tape is includedbetween the two halves 39a and 39b of the tape deck. Obviously, it ispossible to put the two halves together so that the insulating surfacesof the central tapes are in contact. This would mean that the conductivepatterns on the outside tapes of the deck would be exposed and liable todamage as well as the possibility of shorting occurring when the coresare in position. Thus, this arrangement would require an insulating tapeon each side of the tape deck.

The dimensions of the tape 39 described above are typically as follows:

The main portion of the tape which carries the ladder networks (that iswithout the extension lead 53), has a length of approximately eightinches and a breadth of approximately two inches. The extension lead 53is approximately five inches long and has a breadth of a little overhalf an inch. The thickness of the tape which is in this case made ofpolyester terephthalate is three thousandths of an inch.

When a number of tapes 39 are stacked in the store as previouslyexplained, portions of the ladder networks on one tape are separatedfrom the corresponding ladder networks on its neighboring tape by aslittle as three thousandths of an inch, this being the thickness of thetape. Thus, when a current pulse is passed along a selected laddernetwork or winding in the memory during information read out there isinductive and capacitive coupling between this winding and its nearestneighbors which results in damped oscillations or ringing in theselected winding. FIGURE 16 shows schematically a portion of the memorywith a pattern of stored information which particularly aggravates theeffect. Four cores only are shown for the purpose of illustration andare labelled A, B, C, D. Each core has its own sense winding 73 loadedby a low resistance RL and is threaded by one of two primary windings 74and 75. The low resistance RL is chosen so as to minimize the voltagesdeveloped in the primary windings 74 and 75 during reading. In practiceRL is so small that its value, referred to a single turn primarywinding, is negligible in comparison with the leakage react-ance of thetransformer. That is, the impedance measured across a primary winding 74or 75 is the same as if the sense windings 73 were short circuited. Itis assumed that primary winding 74 on one tape and primary winding 75 isin the corresponding position on the next tape in the deck. The patternof information stored to aggravate the ringing in the memory is primarywinding 74 storing 1 O 1 1 0 (which word will be referred to as wordNo. 1) and primary winding 75 storing O 1 0 1 0 1 (which word will bereferred to as word No. 2), the third tape in the deck would be storing1 01 0 l 0 (word No. 1) and the fourth 0 1 0 1 0 1 (word No. 2) and soon, through the store. To digress, the primary windings storing word No.1 thread through alternate cores A, C, E, etc., and the primary windingsstoring word No. 2 thread through the remaining cores B, D, F, etc.

FIGURES 17b and 0 show the output signals received on a sense winding 73in response to an input pulse (FIG- URE 17a) on a primary winding 74 or75 for a stored binary 1 bit or a binary 0 bit respectively. It isapparent from the pulse diagrams of FIGURE 7 that the ringing which isproduced on the secondary winding reduces the ratio of the 1" to 0signals and also the maximum speed of operation. [It is therefore anundesirable effect.

The problem will now be analyzed in. order to provide a. solution. Tosimplify what would be an involved calculation it is assumed that thereis perfect magnetic coupling between all the primary windings in thetape deck and the transformer cores threaded by them but that there isno magnetic coupling between the primary windings themselves. Thus, eachprimary winding behaves as though it were a single conductor and istreated as such in the following analysis.

The capacitive coupling will be greatest when the primary windings areperfectly interleaved as shown schematically in FIGURE 16. Theequivalent circuit of the transformers so Wound is shown in FIGURE 18where PQ represents any one of the primary windings that threads coresA, C, E etc., and RS represents the corresponding primary or an adjacenttape that threads cores B, D, F, etc.

To determine the response to an input current pulse I the signalgenerator G shown in FIGURE 18 is replaced by the three generators G G6;, each of magnitude l/2 I as shown in FIGURE 19. This change is seento be justified by combining the currents at points I, Q, R, and S whenit is seen that the resultant currents in the circuit are still thesame. Consider the response of the circuit to generators G and G only.=From considerations of symmetry these will cause no current to flowacross the capacitance, and so the current in each line, PQ and RS willbe 1/2 1 Now consider the response of the circuit to generator G The twolines and the distributed capacitance between them forms a transmissionline with an open circuit at one end and a short circuit at the otherend. This resonates at a frequency f =1/4LC and its odd harmonics, whereL is the sum of the transformer leakage inductances, and C is the totalcapacitance between PQ and RS. Then, if I is a square pulse, having aninfinite frequency spectrum all the resonant frequencies will appear onthe lines. In practice the rise-time of I is made long enough for itsenergy content at the harmonic frequencies to be negligible incomparison with that at the fundamental, and therefore only thefundamental frequency need be considered.

From the above argument it is seen that any oscillatory current is dueonly to generator G and from the known properties of the transmissionline its magnitude will be greatest at the short-circuit end of theline, that is through transformer cores Y and Z. Consider, therefore,the current through transformer cores Y and Z, caused by G Let thesecurrents be respectively I and 1, These currents will be in oppositedirections, as shown, and but for the negligibly small current I,,, areequal in magnitude.

As far as the voltage and currents at either end of the line areconcerned, the line can be represented at frequencies up to thefundamental frequency (f by a single pi-section as shown in FIGURE 20.The capacitor at the short circuit end carries no current and cantherefore be omitted, resulting in a simple parallel tuned circuit shownin FIGURE 21.

For I to be nonoscillatory the circuit must be critically damped oroverdamped. This can be done by introducing a resistance :R in parallelwith L or a different value of resistance R in series with L where l t mIt must be remembered that, whether parallel or series damping is used,the damping must be associated with individual transformer cores orindividual, primary windings, as the pattern of information stored isnot generally known.

First consider parallel damping. This can be carried out by placing oneach transformer core a short-circuit winding of resistance R /n where nis the total number of transformers in the memory. The damping resistorscan be made in a similar manner to the tapes carrying the primaryconductors. That is, a thin sheet of resistance material such as Eurekais bonded to an insulating tape (for example, a tape of polyesterterephthalate). The tape and 76 and resistive coating are punched asshown in FIG- URE 22 to provide apertures 77 for the transformer coresand etched to leave a resistive loop 78 round each aperture throughwhich the legs of the transformer cores pass. The tape 76 is alsoprovided with a row of sprocket holes 49 for advancers in a processingmachine during the formation of the resistive loops. There is someadvantage in using several such resistive tapes 76 in a memory, spacedevenly throughout the stack of word tapes 39 since this gives bettermagnetic coupling with the cores. However, whether one resistive tape orseveral are used, the resistance of each closed loop 78 should be a R,,/n where a is the number of loops linking one transformer core. As analternative to the resistance tape, the gaps in the copper coating ofeach core can be coated with resistance material, thus providing theresistive loop.

Considering now the series damping, this can be produced by usingresistive primary windings, but where there are many the resistance ofeach would have to be incon veniently high, and very high drivingvoltages would be necessary. For example, if each primary winding had aresistance R then, referring to vFIGURE 18 PQ and RS would each have aseries resistance 2Rw/ m, where m is the total number of words in thememory.

The effective resistance appearing in series with L in FIGURE 21 wouldthen be Rs: 4Rw/m from which Rw=mRs/ 4 In one practical example RS wasapproximately 120 ohms and m was two hundred and fifty-six. This givesRw a value of 7,680 ohms and so for a current of 50 ma. through aprimary winding, a voltage of 384 volts would necessarily have to beapplied.

A better method of series damping is shown in FIG- URE 23. The coresmarked S are the normal read-only store cores which carry the secondarywindings. Each core S has associated with it a second core T, andwhenever a primary winding passes through a core S, it is also takenthrough the associated core T. The effective resistance is introducedeither by using a material with a proper loss characteristic for the Tcores, or by loading them with resistive loops which can be made in thesame way as the resistive loops for parallel damping.

*It has been shown above that the intertape capacitance bears a directrelationship to the ring in the transformer read-only memory. Byreducing this capacitance the ringing frequency can also "be reduced.The capacitance is reduced by manufacturing three types of tapes. Thesetapes are the a tape shown in FIGURE 24, the b tape shown in FIGURE 25and the c tape shown in FIGURE 26. Each of these tapes contains the samefeatures as the tape 39 described earlier with reference to FIGURE 10.Namely, rows of apertures 41, 42, 43 and 44, ladder networks 45, :46, 47and 48 and sprocket holes 49. In these FIGURES 24, 25 and 26 only aportion of each tape is shown, being sufficient for the purpose ofexplanation.

The three tapes, a tape, b tape and c tape are identical in everyrespect except the ladder networks have a different stagger relative tothe rows of apertures in each tape. The stagger is differentlongitudinally and transversely to its length, thus when the tapes areassembled in the tape deck in this order, that is a tape, b tape, tape,a tape, b tape, and so on the distance between adjacent primary windingsis increased with a corresponding increase in capacitance. Theprogramming of the tape is still carried out by punching a small hole tobreak the ladder network on one or the other side of the apertures as isshown in the b tape. An advantage in the programming by punching is thatthe same punch can be used for all three types of tape. Each tape isdistinguished by a ten character figure printed in ink in box 79 on thetape. The characters indicate the tape program, its position in themodule, this being the name given to the complete assembly, and itsstagger.

Having thus far described the principles of the transformer read-onlystore, how these principles are realized in practice, some of thedrawbacks, and how they have been overcome, a description of a completemodule of the store will now be given. In view of the large number ofparts in the complete assembly, the description that follows will begiven with particular reference to four figures, namely FIGURES 27, 28,29 and 30.

FIGURE 27, an exploded view, shows the complete module with the side ofthe assembly carrying the I- shaped parts 14 of the transformer cores.The U-shaped parts 13 are inserted into the array. In view of therestricted size of the drawings no serious attempt has been made to showthe ladder networks on the tapes.

As previously stated the complete module of the transformer read-onlystore consists of one hundred and twentyeight tapes 39 arranged in twohalves separated by an insulating sheet, to form the tape deck.

Each tape 39 in the tape deck carries two information words each ofsixty bit length making a total capacity of two hundred and fifty-sixwords per module. The insulating sheet included between the two halvesof the tape deck is not shown, neither is the resistive tape or tapesprovided to damp ringing oscillations. The tape stagger to reduce thecapacitive coupling between adjacent primary windings is not apparent inthe figures.

The tape deck is mounted in an assembly which consists basically of twoend blocks 82 and 83 which are spaced apart and held rigidly by two rods84 and 85. The two end blocks are generally T-shaped and the rods 84 and85 extend between the ends of the cross-pieces of the Ts so that a rigidrectangle is formed of similar dimensions to the main body of a tape 39,that is the portion of the tape 39 which carries the information word's.Into the underside of the cross-piece of each T-shaped end block 82 and83 (the cross-piece is displaced laterally with respect to the stem ofthe T) is screwed an aligning pin 86. It is onto these two aligning pins86 that the tape deck of the one hundred and twenty-eight tapes 39 ismounted by threading the pins 86 through the sprocket hole at each endof the tapes. The pins are of such a diameter that they just fit thesprocket holes through which they pass so that the tapes are accuratelypositioned with the rows of apertures in precise alignment. In view ofthe fact that the tapes 39 are made of very thin flexible material a supporting tray 87 of an insulating material can be placed over thealigning pins. This tray, which is identical in construction to the mainbody of a tape and has the same punching, provides a firm base for thetape deck, but is not usually necessary since the tapes are. With thetape deck in position on the aligning pins the stern portion of each endblock 82 and 83 provides an abutment for the ends of the main portion ofthe tapes 39. The extension leads 53 from the tapes in the lower half ofthe tape deck pass on one side of the stem of end block 83 and theextension leads from the tape in the upper half of deck pass on theother side.

The rods 84 and 85 also provide supports for the cor carrier assemblies88. The U-shaped parts 13 of the trans former cores are passed throughthe apertures in the tape deck and require no support other than a meansto prevent them from dropping out again. The I-shaped parts 14, on theother hand, have to be held firmly in the correct position so that theymate with the open ends of their respective U-shaped parts 13 and formclosed transformer cores. It is as a support for the I-shaped parts 14that the core carrier assemblies 88 are provided. In the tape deck,apertures are provided for two parallel rows of transformer cores, therebeing thirty cores in each row. Thus thirty core carrier assemblies 88are required, each one to carry the two I-shaped parts for thecorresponding cores in the two rows.

CONCLUDING SUMMARY The invention relates to construction features for a1 3 transformer read-only storage device, and particularly to featuresfor eliminating the problem of oscillatory ringmg.

Stripline conductors mounted on adjacent tapes are staggered to reducemutual capacitance.

Close conductive loops are mounted about individual transformer coresand arranged to provide critical dampingto the capacitances andinductances present.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

1. A transformer read-only storage device having a stack of elongatedinsulating carriers, each carrier having a plurality of apertures spacedapart along its length in at least one row, the carriers being stackedso that the corresponding apertures register with one another; aplurality of magnetic cores passing through said registering apertures;a drive conductor for each row extending continuously along the lengthof the carrier and passing on one or the other side of each aperture inthe row in accordance with a predetermined pattern, and sense windingsone for each core arranged to receive a pattern of signals uponenergization of a selected drive conductor, characterized by a varyingrelative displacement, from the associated row of apertures, of thecorresponding drive conductors on adjacent carriers in the stack in suchfashion that the distance separating a major portion of correspondingconductors on adjacent carriers is greater than the thickness of theintervening carrier, and means mounting a resistance, of criticaldamping value, for the capacitance and inductance present, about each ofsaid magnetic cores.

2. A storage device according to claim 1 wherein said resistance meansis an auxiliary elongated insulating carrier having a plurality ofapertures spaced apart along its length which register with the existingapertures in the stack, and are similarly arranged with said corespassing through the apertures, and a closed loop of resistive materialarranged about each of the apertures in said auxiliary carrier.

3. A storage device according to claim 1 wherein said resistance meansis a coating of resistive material on each of said cores.

4. A storage device according to claim 1, wherein said resistance meansfor each core is a coating of conductive material over all of thesurface of each of said cores with the exception of a narrow annulus oneach core, and said narrow annulus of the surface is coated with a layerof resistive material.

5. A storage device according to claim 1, in which the plurality ofapertures in each carrier extend along the length of the carrier in aplurality of rows in pairs, the drive conductors associated with eachrow in a pair of rows being electrically connected together at one endof the carrier and electrically connected to terminals at the other endof the carrier.

References Cited UNITED STATES PATENTS 3,138,786 6/1964 Smura 340--1743,234,529 2/1966 Hsueh 340-174 3,245,058 4/ 1966 Bruce 340-l74 3,289,17711/1966 Schulte 340-174 OTHER REFERENCES D. N. Taub, The Design ofTransformer (Dimond Ring) Read-Only Stores, IBM Journal of Research andDevelopment, vol. 8, September 1964, pp. 443-457.

TERRELL W. FEARS, Primary Examiner.

JOSEPH F. BREIMAYER, Assistant Examiner.

